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Pontederia cordata
מהויקיפדיה האנגלית thumb|ימין|300px|Pontederia_cordata צולם: Giardino dei Semplici a Firenze Pontederia cordata, commonly known as Pickerelweed, is a monocotyledonous aquatic plant native to North and South America. It grows in a variety of wetlands, including pond and lake margins across an extremely large range from eastern Canada south to Argentina. A few examples include northern rivers,Day, R. T., Keddy, P. A., McNeill, J., and Carleton, T. (1988). Fertility and disturbance gradients: a summary model for riverine marsh vegetation. Ecology, 69, 1044–54. the EvergladesLoveless, C. M. (1959). A study of the vegetation in the Florida everglades. Ecology, 40, 1–9. and Louisiana..Keddy, P. A., Campbell, D., McFalls T., Shaffer, G., Moreau, R., Dranguet, C., and Heleniak, R. (2007). The wetlands of lakes Pontchartrain and Maurepas: past, present and future. Environmental Reviews, 15, 1–35. The species grows as an emergent plant, that is, in flooded conditions, so the plant is generally dependent upon aerenchyma in the stem to carry oxygen into the roots. Its metabolism, is, however, also tolerant of low soil oxygen.Laing, H. E. (1940). Respiration of the rhizomes of Nuphar advenum and other water plants. American Journal of Botany, 27, 574–81. It is often found in areas where water levels fluctuate naturally, with spring flooding and later summer emergence. Apart from flooding, the species is also influenced by soil fertility, tending to grow in the more fertile bays of large lakes, for example. Like many aquatic plants, it is negatively affected by salinity and grazing.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p It is also negatively affected by competition from other wetland plants.Geho, E. M., Campbell, D., and Keddy, P. A. (2007). Quantifying ecological filters: the relative impact of herbivory, neighbours, and sediment on an oligohaline marsh. Oikos, 116, 1006–16. Like many wetland plants, it can survive infavorable conditions as buried seeds in the soil.Whigham, Dennis F. and Robert L. Simpson. 1982. Germination and dormancy studies of Pontederia cordata L. Bulletin of the Torrey Botanical Club 109: 524-528. The plant flowers in late summer. The purple flowers have yellow markings which may assist in attracting bees for pollination.Sculthorpe, C. D. (1967). The Biology of Aquatic Vascular Plants. Reprinted 1985 Edward Arnold, by London. p. 280. One bee species known to pollinate the flowers is Dufourea (Halictoides) novaeangliae.Hutchinson, G. E. (1975). A Treatise on Limnology, Vol. 3, Limnological Botany. New York: John Wiley. p.229. Once the plant begins to produce seeds, the stem supporting the infloresence bends to submerse the fruits and seeds.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Figure 6.9. Seeds are dormant at the time of dispersal and will not germinate without stratification for 6-8 weeks.Whigham, Dennis F. and Robert L. Simpson. 1982. Germination and dormancy studies of Pontederia cordata L. Bulletin of the Torrey Botanical Club 109: 524-528. The flowers of the species are tristylous, meaning the styles of individual plants occur in three different morphs, with most populations containing all three. Leaf shape, which varies considerably across populations, within populations, and even within individuals, has been the source for many taxonomic synonyms. Like many wetland and aquatic plants, the species can reproduce asexually by means of branching rhizomes, and hence can form large clonal stands.Hutchinson, G. E. (1975). A Treatise on Limnology, Vol. 3, Limnological Botany. New York: John Wiley. References External links *[http://plants.usda.gov/java/profile?symbol=POCO14 PLANTS Profile for Pontederia cordata] *[http://planthardiness.gc.ca/ph_spp_intro.pl?speciesid=1005338 Pontederia cordata], Natural Resources Canada *Pontederia cordata Flowers in Israel קטגוריה:קומלינאים